Saturday, 2 July 2011

Signs and symptoms

Signs and symptoms

Burns

Second-degree burn after a high tension line accident

Heating due to resistance can cause extensive and deep burns. Voltage levels of 500 to 1000 volts tend to cause internal burns due to the large energy (which is proportional to the duration multiplied by the square of the voltage divided by resistance) available from the source. Damage due to current is through tissue heating. It is a relatively unknown fact that more electrical workers die from burns than from an electric shock. In fact, only around 20% of deaths are the result of electric shock.[5]

Ventricular fibrillation

A domestic power supply voltage (110 or 230 V), 50 or 60 Hz AC current through the chest for a fraction of a second may induce ventricular fibrillation at currents as low as 60 mA. With DC, 300 to 500 mA is required.[2] If the current has a direct pathway to the heart (e.g., via a cardiac catheter or other kind of electrode), a much lower current of less than 1 mA (AC or DC) can cause fibrillation. If not immediately treated by defibrillation, fibrillations are usually lethal because all the heart muscle cells move independently instead of in the coordinated pulses needed to pump blood to maintain circulation. Above 200 mA, muscle contractions are so strong that the heart muscles cannot move at all.

Neurological effects

Current can cause interference with nervous control, especially over the heart and lungs. Repeated or severe electric shock which does not lead to death has been shown to cause neuropathy. Recent research has found that functional differences in neural activation during spatial working memory and implicit learning oculomotor tasks have been identified in electrical shock victims.[6]
When the current path is through the head, it appears that, with sufficient current,[clarification needed] loss of consciousness almost always occurs swiftly. (This is borne out by some limited self-experimentation by early designers of the electric chair[citation needed] and by research from the field of animal husbandry, where electric stunning has been extensively studied.)[7]